One definition of cloud computing is network-based services which appear to be provided by virtual hardware running on one or more real machines. Typically, cloud-based services run on multiple connected computers, often over a real-time network such as the Internet. A cloud image is a file that contains the contents of an operating system (OS) plus additional software that can be instantiated on a cloud management system as one or more running virtual computing nodes, commonly called “instances.” One advantage of using cloud images is that a system may be shut down and restored later to the exact same state. Cloud management systems such as AMAZON EC2® and IBM SMARTCLOUD® employ cloud images as a basic unit of deployment.
A cloud-based service is simply a collection of one or more virtual machines that work together to provide some capability to a deploying organization or its clients. Benefits of cloud images in conjunction with cloud-based services may include 1) as fixed configuration that can deploy in a reliable and consistent manner; and 2) well-known optimization techniques such as copy-on-write that can lead to very fast instance deployment times and reduced storage costs.